Radioactive Half-Life Calculator

Calculate how much of a radioactive substance remains after a given time, using the concept of half-life.

Half-life
(time units)

Example: years, days, seconds — unit doesn’t matter.

Elapsed time
(same units)

Must use the same units as half-life.

Initial amount
(optional)

Can be grams, atoms, %, etc.

Remaining amount

—

Decayed amount

—

Lost due to decay

Half-lives passed

—

Remaining fraction = (1/2)^{t / T½}

This model assumes ideal exponential decay without external influences.